Curing and rheological behavior of vinyl ester resins prepared in the presence of tertiary amines

Vinyl ester resins V-1, V-2 & V-3 of acid value (similar to 6 mg KOH g(-1) solid) were synthesized using bisphenol-A epoxy and acrylic acid in the pre sence of triethyl-, tripropyl- and tributyl-, amines in 210, 270 and 340 mi nutes, respectively. The synthesized resins were characterized by FTIR spec troscopy and a new peak at 2360 cm(-1) was observed which is due to attachm ent of amines to resin structure by hydrogen bond. The curing behavior of s ynthesized resin containing 40% styrene (w/w) and 2% benzoyl peroxide was s tudied using DSC technique and found to be affected by presence of amines. Activation energy and frequency factor for the curing reaction increases fr om 14 Kcal mol(-1) to 23 Kcal mol(-1). Rheological behavior of resins conta ining 40% styrene was studied using a Haake Rotovisco RV20 viscometer, and viscosity was found to increase with shear rate up to 200 sec(-1). The aver age values of activation energy at constant shear stress (6-15 Pa) were 12. 94, 13.20, 13.70 Kcal mol(-1) for V-1, V-2 and V-3, respectively. The activ ation energy at constant shear rate decreases with an increase in the shear rate.